Chair base



FIG. 1 is a perspective view of a chair base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a side elevational view, the opposite side being a mirrorimage thereof;

FIG. 4 is a top plan view thereof; and

FIG. 5 is a rear elevational view thereof.

In order to illustrate the environment in which the claimed design isused, exemplary wheels are shown in phantom. The wheels form no part ofthe claimed design.

The ornamental design for a chair base, as shown and described.